Products made from expanded polystyrene foam are highly valued. For example, preformed polystyrene foam components are favored in construction because they are lightweight and easy to install. Polystyrene can provide excellent thermal insulation and can be molded into a variety of shapes. Polystyrene foam would be a material of choice in making shower and bathroom components, especially when irregularly shaped items are needed, but for the fact that the material is not water-resistant. Further, ceramic tiles, natural stone tiles and other decorative materials commonly used in showers and bathrooms do not adhere well to polystyrene foam products.
Various attempts have been made to create a water resistant coating for expanded polystyrene products. For example, latex-based coatings have been used. But while such coatings improve water resistance of polystyrene foam to some degree, they are not water-resistant enough. Further, such latex-based coatings have inferior durability performance including poor scratch and UV resistance and do not necessarily improve the adhesive properties of polystyrene products, especially when tiles are selected for attachment to the products. Furthermore, the latex-based coatings tend to be significantly more costly than the water-resistant coatings of this invention. Finally, polystyrene is sensitive to certain hydrocarbon solvents, and many organic compounds are unsuitable for use on polystyrene as they may cross-react and damage the surface of a polystyrene product.
Thus, there remains a need in the field for preformed polystyrene products with improved water resistance and adhesion for tiles and other decorative materials. Because curved and generally irregular shapes of various shower components are laborious to paint, there also remains a need in the field for improved coating formulations that can be spray-coated on such shower components.